Display technology is expected to become a dominant sector of high-tech industry in the future. It is also expected that the flat panel display technology will be revolutionized by the use of organic semiconductors that will allow manufacture of cheap, flexible, lightweight, fully portable flat panel displays with no apparent limits to their size. It is predicted that due to the lower manufacturing cost, organic semiconductor based displays will eventually gain dominance over amorphous silicon based counterparts and the respective market share will grow to $1.6 billion by 2007. To realize these goals, however, significant breakthroughs will have to take place in the area of organic semiconductor material and device processing.
Interest in organic thin film transistors (OTFTs) for possible use in displays, sensors and other large area electronic applications has been increasing rapidly. Best reported organic thin film transistor (OTFT) device performance rivals or exceeds that of hydrogenated amorphous silicon devices, and low OTFT process temperatures allow fabrication on a range of surfaces including cloth, paper or lower temperature polymeric substrates.
Organic semiconductors for use in OTFTs can be broadly divided into two groups as high and low mobility materials. High mobility materials have mobility >0.1 cm2/V-s, usefully large carrier energy bandwidth (>0.1 eV) and weak or sometimes absent temperature activation of mobility. To date, most high mobility organic semiconductors have been small molecule materials (with pentacene the most notable example) and most have been deposited by vacuum sublimation or from a solution precursor with a high-temperature (>150° C.) conversion step. Low mobility materials have mobility from about 10−5-10−1 cm2/V-s, typically transport carriers by hopping, and have strong temperature activation of mobility. Most polymeric organic semiconductors fall into this group and many have the potential advantage that they can be deposited from solution.
To date, there have been few reports of low-temperature solution processed organic semiconductors with high mobility. In addition, even for low mobility materials, current solution deposition techniques have not demonstrated material structure, thickness and property control comparable to vacuum deposition techniques. The present invention relates to new organic semiconductor compounds with relatively low OTFT process temperatures and relatively high mobility.